Minor corrections: don't write MRT, write MTR. MRT is in Singapore and you didn't take that train!Payment is available in Chinese yuan only. Hong Kong dollars are not accepted, however there are currency exchange there and ATMs. The port visa is ONLY available at Lo Wu. Lok Ma Chau, Shenzhen Bay ...

you don't need to dress up. Wear whatever you'd wear in public already. Most business class cabins offer very private seats - you're not in display, it does not matter.  If you can wear it into the qantas club, you can wear it in business or first. 

bingo. the busses will be fun. like what QF did briefly at T4 

Here's everything that'll happen in LAX: https://www.lawa.org/newsContentbs.aspx?ID=2311

longer than MCT. If MCT is 120, your layover must be 120 or greater